Volvo Maintenance Hints for 7xx/9xx - Bill Garland's Nuclear ...

PROBLEM AREAS
A common problem with a turbocharger is oil passing by the oil ring
seals, leaving a cloud of blue smoke coming from the exhaust. The
oil drain inside the unit could be plugged with coke/burnt oil
deposits, making the only route for the oil is to dump into the
exhaust. Oil must be drained away from the turbo faster than the oil
being fed to it. Consider the possibility that excessive oil pressure/
volume might be being fed to the turbo, causing the bearing
housing to be flooded with oil and the turbo to leak.
• A restricted air inlet;
• A restricted exhaust;
Turbochargers won’t actually blow a seal; the seal on the
exhaust side is usually a simple piston ring with a small ring gap.
The seal on the compressor side is either the same style or a
more positive carbon seal similar to an air conditioner
compressor seal, or even a water pump seal. Before you
condemn the turbo, consider the fact that even a good turbo will
leak oil given certain circumstances. Here are four areas to look
at:
• A physical restriction in the oil drain away from the turbo; and
• An effective restriction to the oil drain away from the turbo, such as crankcase ventilation
problems or anything that can cause excessive crankcase pressure, like worn piston rings.
In this article, I am going to try to give you some pointers in rebuilding the most popular Volvo
turbo units. Volvo used the Garrett T3 unit for some years with great service results. It was
used in the 240 series and the 760, and then the water-cooled units were available.
REBUILD PROCEDURES
1. Remove turbocharger from manifold and place it on a clean workspace.